Actually guns DO work in the wizarding world because it's only electronic components that get fucked up by magic. But there's the matter of most wizards believing that muggles haven't evolved since the fucking 1300's, and therefore discrediting every bit of technology from muggles. And I guess Harry didn't go get a gun because he was a 17 year old at the end of the series and you can't buy guns without a license in the UK. And you have to be 18 for a gun license.

If guns stopped working around magic then the human body would likely stop working around magic too.
Guns work on springs, linkages, and chemical reactions. The human body works on very specific chemical reactions, to the point that if enough of the water in your body was replaced with deuterium oxide (heavy water) you would die.
The reactions in guns are relatively simple compared to the reactions in the human body, so the human body would likely fail before guns do.

Around places like Hogwarts, Hogsmeade and Diagon Alley where there's a fuckton of wizards/witches then they don't work. But when there's only one (so Harry at the Dursley's, it doesn't have the same effect)

Actually guns DO work in the wizarding world because it's only electronic components that get fucked up by magic. But there's the matter of most wizards believing that muggles haven't evolved since the fucking 1300's, and therefore discrediting every bit of technology from muggles. And I guess Harry didn't go get a gun because he was a 17 year old at the end of the series and you can't buy guns without a license in the UK. And you have to be 18 for a gun license.